My understanding is this: (And everything I am saying is a matter of opinion)
Might be "Missing" in your process is Decoction Mash will draw the Melanoidin flavor out of your Pils/Vienne/Melanoidin malt, failing to do this process wastes the grain. Debatable in many styles, however, in Munich Helles I think it is a must.
To read about that:http://byo.com/hops/item/537-decoction-mashing-techniques
And I def. think that it would require you to use a triple decoction mash to fully capture the "Helles flavor" out of your Pils and total grain bill.
The style does not carry Munich Malt. (weird right) Here is were It becomes strange, I understand that it is a Munich style, the original is said not to have munich malt. Crazy Right? So I am told/read that Munich Malt will muddle or muddy up the rich pilsner flavor, because it is delicate and can be overpowered. Pale ale malt is too thick on your palate and should not be used in the style. At least (so I read) no more than 3% of pale ale malt.http://byo.com/mead/item/747-helles-style-profile
for the nay say to Munich malt in the style.
So because of that, the only experience I have had was not my own beer, but a brew session with a friend that got me into the hobby.
We did this.Grain
1.25% Honey (arguably not a part of the style but overall flavor was on)
6.25% Candi Sugar (attempt of an Helles Export rather than the traditional)
So here in lies the argument for me: Yeast, and ABV for a Helles
So there is Helles, Helles Export, Spezial Helles, EdelHelles, Urhelles, Urtyphelles, etc... They all have subtle variations. Traditionally (I believe) Helles, Helles Export, Urhelles, and Urtyphelles did not included any Munich malts. They are only Pils. However the Spezial (Seasonal Breweries Best so to speak) may have included anything the brewery wanted to use that was in season. Edelhelles however was the noble variety of the style, or to remind the consumer of the "lofty, noble rank of the beer hops"
To read more on where I am getting all of that :http://byo.com/mead/item/747-helles-style-profile
So Yeast to me was a big factor from what was used around that time frame, and what was popularly used in 1894. Which leans me to learn about Muller Thurgau who was able to isolate the single yeast cell for wine and beer fermentation. So probably multiple yeasts used to "Birth" the helles style. So it would be difficult to really match what breweries that have 100+years of tradition. So possibly a variety of Bavarian Yeasts were used, that were probably funky, fruity, bubblegum, clove, and dark spice characters.
With all of this being said, I think you have to brew to your taste. Trial and "error", is just the excuse to tell your wife you gotta make another batch right?